This has been coming for a while. It started with the Shanghai market crashing a few weeks ago, and the government there trying to prop it up. It worked for a little while, but is now on its downward slide again.
I've been moving most of my retirement money out of stocks over the last few months, and am practically all in cash at this stage.
I wouldn't be getting into anything just yet. The North American markets have potential to slide quite a lot further than they have. To give you some perspective, the Shanghai market is now down over 40% from its peak, and I'll be surprised if it doesn't have at least another 20% (from here) to drop, and maybe as much as another 40% (which will take it down about 67% from its peak). Put the North American 10% slide beside this and there could be a way to go yet. Then again, I might be wrong... but I did manage to liquidate ahead of 2008 as well as the current decrease (most of my holdings are in Asia rather than North America).
Currencies have also taken a hit. The New Zealand dollar slid 8%, and Canadian dollar slipped as well.
I wouldn't be surprised to see oil (and other commodities) go lower from here before they start to recover. There is an oil glut out there, which combined with the slowdown in the Chinese economy, means that low oil prices will last for a little while at least.